1. Field of the Invention
The present invention relates to a steam generator for a liquid metal reactor and a heat transfer method thereof, and more particularly to a steam generator for a liquid metal reactor having three different fluids with forced circulation and an improved tube bundle configuration therein, and a heat transfer method of such a steam generator, whereby the sodium-water reaction accident is prevented while sodium is still used as the primary coolant and heat transfer efficiency is improved.
2. Description of the Related Art
A liquid metal reactor is a nuclear reactor which generates heat using fast neutrons for nuclear reaction. The liquid metal reactor uses liquid metal, not water, as a coolant.
An example of such a conventional liquid metal reactor is schematically shown in FIG. 9.
In the liquid metal reactor as shown in FIG. 9, sodium, which is a coolant, is heated as it passes through a reactor core 100. The heated sodium is circulated through a sodium-circulating piping 101. At this time, heat is transferred from the heated sodium to water in a steam generator 300. The resulting steam operates a turbine 400.
If a heat transfer tube in the steam generator 300 leaks, the water from the leakage inevitably comes to react with sodium violently. In order to prevent such an accident of the sodium-water reaction, an intermediate heat transport system composed of intermediate heat exchangers 200 and intermediate heat piping 201 is provided between the primary heat transport system of the sodium-circulating piping 101 and the steam generation system of the water-circulating piping 301.
Consequently, a first heat transfer is accomplished from the sodium circulated through the sodium-circulating piping 101, which is heated as it passes through the reactor core 100, to the sodium circulated through the intermediate heat piping 201 in the intermediate heat exchanger 200. Subsequently, a second heat transfer is accomplished from the sodium circulated through the intermediate heat piping 201 to water circulated through the water-circulating piping 301 in the steam generator 300. The resulting steam operates the turbine 400.
As described above, the conventional liquid metal reactor includes the aforesaid intermediate heat transport system to protect the reactor core from an accident of the violent chemical reaction of water and sodium when a tube in the steam generator 300 leaks water. Nevertheless, the possibility of the accident of the sodium-water reaction still exists. Besides, the installation of the intermediate heat transport system increases the construction cost of a liquid metal reactor plant.
In order to solve the aforesaid problems, another conventional liquid metal reactor having a simple structure has been proposed. An example of the conventional liquid metal reactor is schematically shown in FIG. 10.
As shown in FIG. 10, the liquid metal reactor comprises: a high temperature piping 101 through which heated liquid metal is circulated, the high temperature piping 101 communicating with a reactor core 100; coiled high temperature heat transfer tubes 102 connected between one end of the high temperature piping 101 and the other end of the high temperature piping 101; a low temperature piping 301 through which water is circulated, the low temperature piping 301 communicating with a turbine 300; coiled low temperature heat transfer tubes 302 connected between one end of the low temperature piping 301 and the other end of the low temperature piping 301; and a steam generator 200 having a container 201 in which the coiled high temperature heat transfer tubes 102 and the coiled low temperature heat transfer tubes 302 are installed. An intermediate heat transfer fluid 202 is filled in the container 201.
In the liquid metal reactor constructed as mentioned above, heat transfer from the high temperature fluid flowing inside the tubes 102 to the low temperature fluid flowing inside the tubes 302 in the container 210 of the steam generator 200 is accomplished by heating the intermediate heat transfer fluid 202 by the high temperature fluid in the tubes 102 and naturally circulating the intermediate heat transfer fluid 202.
A fluid chemically stable to both water and sodium is used for the intermediate heat transfer fluid 202.
The aforesaid liquid metal reactor naturally circulates the intermediate heat transfer fluid 202 and is supposed to achieve the required heat transfer without the possibility of the accident of the sodium-water reaction by using the intermediate heat transfer fluid 202 which is chemically stable to both water and sodium.
Although the accident possibility is removed, the aforesaid natural circulation does not provide sufficient heat transfer performance and its heat transfer efficiency becomes remarkably low.
The heat transfer area of the steam generator must be sufficiently increased to prevent the aforesaid reduction of the heat transfer efficiency, and thus to obtain desired heat transfer efficiency. In this case, the size of the steam generator is impractically increased, which leads to an increase of the cost of manufacturing the steam generator.
Increasing the size of the steam generator inevitably involves increasing the size of a containment dome, in which the steam generator is installed.
In conclusion, operation of the liquid metal reactor using the natural circulation type steam generator without the previously mentioned intermediate heat transport system becomes impractical.